Wind data for the Pacific Ocean obtained by NASA's Quick Scatterometer
spacecraft -- also know as Quikscat -- are documenting episodes of
reversed trade winds that are responsible for unseasonable cyclone
conditions in the northwest and southwest Pacific, and which may be a
precursor of a future El Niño.

A research team led by Dr. W. Timothy Liu, a senior research scientist
at NASA's Jet Propulsion Laboratory in Pasadena, Calif., used wind
speed and direction data from Quikscat to detect a shift in the trade
winds on February 25. The winds shifted from their normal easterly
direction to a westerly direction, blowing from Indonesia toward the
Americas along the equator. This trade wind shift, which lasted for
about a week, contributed to the spawning of twin cyclones--Super
Typhoon Mitag, which threatened the Philippines; and Tropical Cyclone
Des, which passed through New Caledonia.

"In addition to unusual cyclonic activity, such trade wind reversals
typically trigger Kelvin waves of warm water, which can be an early
indicator of future El Nino conditions," said Liu. "During periods of
reversed trade winds, which typically last from a few days to a week
or more, equatorial westerly winds generate a counterclockwise vortex
in the northern hemisphere and a clockwise vortex in the southern
hemisphere. Once spawned, the resulting Kelvin waves may travel
across the Pacific and reach the coastline of the Americas in
approximately one to two months, warming the waters of the eastern
Pacific and creating El Niño conditions when the effects are
accumulated."

Sustained Kelvin wave activity could have a major impact on global
weather patterns according to JPL oceanographer Dr. William Patzert.
"If trade wind patterns continue to experience reversals through the
spring and summer, the resulting strong, warm Kelvin waves will cross
the Pacific like a conveyor belt, depositing warm water near South
America where the ocean is normally cold," he said. "Such a 'warm
pool' could alter weather all over the planet, with rains that would
normally soak the western Pacific shifting toward the Americas, and
places such as Indonesia and India becoming drier. We're really in a
'wait and see' situation at this point."

A similar westerly wind flow and twin cyclones were documented by Liu
and his team using Quikscat data last December. The wind reversal at
that time, which lasted 10 days, triggered a Kelvin wave that just
recently reached South America, as revealed by NASA's Topex/Poseidon
satellite.

In recent years, data from JPL's Quikscat scatterometer have proven
useful in improving forecasts of extreme wind events, such as
hurricanes, and in monitoring longer-term climatic effects such as El
Niño. Quickscat's SeaWinds scatterometer instrument is a
specialized microwave radar that continuously measures both the speed
and direction of winds near the ocean surface in all weather conditions.

The U.S.-French Topex/Poseidon mission has been making precise
measurements of ocean surface topography since 1992. These data are
used to map ocean currents, improve the understanding of ocean
circulation, measure global sea level change and improve global
climate forecasts. Topex/Poseidon's ability to measure sea-surface
height has made it an invaluable tool for studying ocean events such
as El Niño, its little sister La Niña and the much larger and
longer-lasting ocean event called the Pacific Decadal Oscillation.
Topex/Poseidon is managed by JPL for NASA's Earth Science Enterprise,
Washington, D.C.